(Newser)
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Mei Xiang's latest pregnancy has turned out to be another fake, disappointed zookeepers at the National Zoo say. The panda showed all the signs of pregnancy—including elevated hormone levels, building bamboo nests, and cradling objects as if they were cubs—but tests have revealed that she isn't really pregnant, LiveScience reports. This is Mei Xiang's fifth false pregnancy.

Pandas, for reasons scientists don't fully understand, often go through "pseudo-pregnancies" after their once-a-year ovulation. "We're hugely disappointed," a zoo spokeswoman tells the Washington Post. "My colleagues go through herculean efforts when it comes to panda reproduction, so it's very puzzling and extremely disappointing that we didn't have a cub this year."